Semantic Sensor Network Incubator Group Charter

Scope

As networks of sensors become more commonplace there is a greater need for the management and querying of these sensor networks to be assisted by standards and computer reasoning. The OGC's Sensor Web Enablement [1] activities have produced a services-based architecture and standards, including four languages for describing sensors, their capabilities and measurements, and other relevant aspects of environments involving multiple heterogeneous sensors. These standards assist, amongst other things, in cataloguing sensors and understanding the processes by which measurements are reached, as well as limited interoperability and data exchange based on XML and standardized tags. However, they do not provide semantic interoperability and do not provide a basis for reasoning that can ease development of advanced applications.

Ontologies and other semantic technologies can be key enabling technologies for sensor networks because they will improve semantic interoperability and intergration, as well as facilitate reasoning, classification and other types of assurance and automation not included in the OGC standards. A semantic sensor network will allow the network, its sensors and the resulting data to be organised, installed and managed, queried, understood and controlled through high-level specifications. Sensors are different to other technologies, such as service-oriented architecture, because of the event based nature of sensors and sensor networks and the temporal relationships that need to be considered. Further, when reasoning about sensors the various constraints, such as power restrictions, limited memory, variable data quality, and loosely connected networks need to be taken into account

The SSN-XG will work on two main objectives:

The first objective, ontologies for sensors, will provide a framework for describing sensors. These ontologies will allow classification and reasoning on the capabilities and measurements of sensors, provenance of measurements and may allow reasoning about individual sensors as well as reasoning about the connection of a number of sensors as a macroinstrument. The sensor ontologies will, to some degree, reflect the OGC standards and, given ontologies that can encode sensor descriptions, understanding how to map between the ontologies and OGC models is an important consideration. According to W3C recommendations [2], OWL-DL will be the preferred language for ontology specification. The SSN-XG will also investigate mapping between OGC standards and OWL specifications of sensors.

The second objective of semantic annotation of sensor descriptions and services that support sensor data exchange and sensor network management will a serve similar purpose as that espoused by semantic annotation of Web services. We will use as an input for this objective ongoing work on SML-S [3] which in turn borrows from the SAWSDL [4] (also a W3C recommendation) for semantic annotation of WSDL-based Web Services, and SA-REST for semantic annotation for RESTful services [5].